1. Field of the Invention
The present invention relates to a cap for a hub unit and also to a hub unit for an axle of an automobile. More particularly, the present invention aims at reducing the number of parts required for a hub unit that is used to rotatably support an axle of an automobile with respect to a suspension system, thereby lowering the production cost of the hub unit.
2. Description of the Prior Art
An axle of an automobile is rotatably supported with respect to the car body, by a suspension system, by means of a hub unit having a structure such as that shown in FIG. 5.
Referring to FIG. 5, reference numeral 1 denotes a hub which has a flange 2 rigidly secured to the outer peripheral surface thereof to secure a wheel, and an inner ring 3 is fitted on the hub 1. A plurality of rows of outward race ways 4 are formed on the outer peripheral surfaces of the hub 1 and the inner ring 3. Reference numeral 5 denotes an outer ring, which is supported by a suspension system through a mounting flange 6 that is provided on a part of the outer peripheral surface thereof. The outer ring 5 has a plurality of rows of inward race ways 7 formed on the inner peripheral surface thereof.
The reference numeral 8 denotes rolling elements, which are disposed in between the outward race ways 4 formed on the outer peripheral surfaces of the hub 1 and the inner ring 3 and the inward race ways 7 formed on the inner peripheral surface of the outer ring 5, thereby enabling the hub 1 to be rotatable inside the outer ring 5.
A cylindrical space 9 is defined between the inner peripheral surface of the outer ring 5 and the outer peripheral surface of the hub 1. The opening at one end (the opening at the left-hand end as viewed in FIG. 5) of the cylindrical space 9 is closed with a sealing member 14, while the opening at the other end is closed with a hub cap 10 that is firmly fitted into the opening at the other end (the right-hand end as viewed in FIG. 5) of the outer ring 5, thereby preventing dust from entering the cylindrical space 9 and also preventing the grease in the space 9 from leaking to the outside.
The hub cap 10 is formed into a cup-like configuration from a metallic plate, for example, a stainless steel plate, by means of drawing. The hub cap 10 has an outward flange-shaped stopper 11 formed on the outer peripheral surface thereof. With the outer diameter being elastically contracted, the forward half (the left-hand half as viewed in FIG. 5) of the hub cap 10 is forced into the end portion of the opening in the outer ring 5 until the stopper 11 abuts against the end face of the outer ring 5, thereby securing the hub cap 10 to the opening at the right-hand end of the outer ring 5, and thus closing the opening at this end.
Further, an annular partition member 12, known as a slinger, is disposed between the outer ring 5 and the hub cap 10 in such a manner that the outer peripheral edge of the partition member 12 is secured to the inner peripheral surface of the outer ring 5 at the inward race way 7 that is closer to the right-hand end (as viewed in FIG. 5) of the outer ring 5, thereby preventing the grease in the space accommodating the rolling elements 8 from flowing out into the space 13 in the hub cap 10.
The above-described conventional hub unit suffers, however, from the following problems. Since the partition member 12 is independently provided to prevent the grease in the space accommodating the rolling elements 8 from flowing out into the space 13 in the hub cap 10, the number of parts required to constitute the hub unit is increased, so that the parts handling and assembling operations are complicated and the production cost of the hub unit is unavoidably increased.
It is possible to omit the partition member 12 if the amount of grease filling the space between the inner peripheral surface of the outer ring 5 and the outer peripheral surface of the hub 1 is increased so that, even if the space 13 is filled with grease, a sufficiently large amount of grease is present in the space accommodating the rolling elements 8. This practice is, however, not preferable since an excessive amount of grease must be used instead.